Drawing Lesson 16, Part 3 – Shoulder and Arm

Shoulder and Arm – Human anatomy for fine artists

Video Lesson Description

In this video part, you will discover the shoulder and arm anatomy.

Shoulder and Arm Anatomy

The shoulder and arm bones belong to the upper region of the appendicular skeleton.

In this video part, I will talk, in particular, about three bones from the shoulder and arm region:

– The clavicle or collar bone

– The scapula bone – or shoulder blade

– The humerus – the bone of the upper arm

The shoulder girdle includes the clavicles, the scapula bones and the manubrium of the sternum. The clavicle bone is connected to the manubrium of sternum by the sternal end, which is the medial end.

The acromial end or lateral end of the clavicle is connected to the acromion of scapula.

In the shoulder and arm anatomy, the elongated clavicle bone has a twisted S-shape when viewed from above. This bone lies just below the skin and can be felt from one end to another. The curves of this bone are quite individualistic and can vary from person to person. Right-handed people have the right clavicle more curved than the left one. The length of the clavicle determines the width of the shoulders.

The arm is the portion of the upper limb above the shoulder. This portion of the shoulder and arm section has a single bone called the humerus. It is a long bone, which fits into the glenoid cavity of the scapula.

The cross-section of the humerus’ shaft is almost cylindrical beneath the upper head; it becomes triangular further down, and flattens and curves toward the lower end.

The shoulder blade or scapula has a triangular shape. When the arms are hanging down along the torso, the inner edges of the scapula bones or medial borders are almost vertical.

The scapula bone moves when the arm moves. For example, the arm lifted upward causes the scapula to rotate and tilt. You can see how the inside border of the scapula is rotated at an angle marked by the dotted line. The clavicle bone is also rotated; its outer or lateral end is lifted up.

Other movements of scapula bones include:

– Protraction or abduction – when the arms are pushing forward, the scapula bones roll over the ribcage away from the spine.

– Retraction or adduction – when the arms are pulling backward, the scapula bones come closer to the spine.

– Elevation – when the shoulders are pushing upward into a shrug, the scapula bones go upward, as well.

– Depression – when the shoulders are pushing downward, the scapular bones follow this downward movement.

In the shoulder and arm anatomy, the scapula bone has an intricate structure. It is positioned between layers of muscles and is slightly curved along the posterior or back side of the ribcage. Vertically, it spans from the second to the seventh rib. It has two broad planes facing the ribcage and the skin.

The body of the scapula is also called ala or wing; it is thickened around the borders and very thin in the middle.

The upper third of the scapula is located deep inside of the flesh and does not protrude on the shoulder’s surface.
Other parts of the scapula bone as seen from the anterior view are:

– The superior angle

– The inferior angle

– The vertebral border

– The glenoid cavity

– The infraglenoid tuberosity

– The coracoid process

– The acromion process

The bone of the shoulder and arm region, humerus is covered in flesh from all sides and only comes close to the surface on the elbow.

The head of the humerus has spherical shape like a ping-pong ball cut in half and tilted to the side, which sits in the socket of the shoulder blade.

The shoulder and arm anatomy features the greater tubercle of the humerus bone, which is the most lateral point of the entire skeleton. Nearby is the lesser tubercle. Between the greater and lesser tubercles, there is the inter-tubercular groove also known as the bicipital groove, which carries the long tendon of the biceps brachii muscle.

At the elbow end of the humerus, the bone widens up, forming the lateral epicondyle and the medial epicondyle.

In the shoulder and arm anatomy, between the lateral and medial epicondyles there are two bony structures, called the capitulum and the trochlea, which are part of the elbow joint. The capitulum has a rounded shape, while the trochlea is spool-shaped. The intricate shape of the elbow end of the humerus enables the arm not only to bend, but also allows a rotating movement to the forearm.

Please note that the bone of the arm, humerus, reaches the lower end of the ribcage. Keep this mind when making a drawing of a model and deciding where the elbow’s location will be.

Let’s examine the elbow structure of the shoulder and arm region.

Have a look on this three-dimensional model how the humerus joins with the bones of the forearm.

The two bones of the forearm are called the ulna and the radius. The joint between these two bones and the humerus is the elbow joint.

The upper end of the ulna is similar in construction to a crescent wrench grasping a spool. Such a joint creates a ‘hinge’, which allows for flexing and extending of the arm.

The head of the radius is wheel-shaped and connects with the capitulum, which has a round shape (as indicated on this drawing). A ligament encases the head of the radius, and the radius can rotate freely within it, creating a pivot joint. This joint allows for the pronation and supination of the arm.

If you bend your arm at the right angle, so your arm is along the torso, while your forearm is parallel to the ground, and turn your palm upward, as if you are holding a bowl of soup, this would correspond to the supination position. In this position, the ulna and radius are parallel to each other. The palm facing downward creates the pronation position; at which the radius is crossing above the ulna in “X” configuration.